1. Field of the Invention
The present invention relates to an ink pack for sealing an ultraviolet curable ink therein.
2. Description of Related Art
An ink pack is known as disclosed in JP-A-2000-238291. FIG. 12 is a breakaway view illustrating an example of the ink pack of related art. An ink pack 900 includes a surface portion 902 formed of a pair of upper and lower first films 901, and a side-surface portion 904 formed of a pair of left and right second films 903. The surface portion 902 has a laminate structure of a polyethylene layer, a polyester layer, an aluminum layer, and a polyester layer. The side-surface portion 904 has a laminate structure of a polyethylene layer, an aluminum layer, and a nylon layer.
The body of the ink pack 900 is formed by heat fusion. Specifically, the base layer (polyethylene layer) at longer-side portions 905 of the surface portion 902 is heat fused with the opposing base layer (polyethylene layer) at longer-side portions 906 of the side-surface portion 904. Similarly, the opposing polyethylene layers of the surface portion 902 are heat fused at the shorter-side portions (not illustrated) on one side of the surface portion 902. An ink supply opening 907 is provided on the other side of the surface portion 902. FIG. 13 is a partially magnified cross sectional view of the ink pack shown in FIG. 12. As illustrated in the figure, the base layers are exposed on an end surface 910 at a joint portion 908 where the longer-side portions 905 are heat fused to each other.
There has been significant increase of ink consumption in inkjet printers, and the amount of ink sealed in an ink pack has been increasing in proportion. The larger ink amount requires a fair amount of strength in the ink pack itself, particularly at the heat fused portion. At present, the film base layer is provided as a 150 μm- to 200 μm-thick layer to ensure sealing of the ink at the joint portion while maintaining strength for the whole ink pack.